The Geological Time Scale
the “calendar” for events in Earth history
What is The Geological Time Scale...
The geologic time scale is the “calendar” for events in Earth history. It subdivides all time into named units of abstract time called—in descending order of duration—eons, eras, periods, epochs, and ages.
It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history.
humans are currently in the Cenozoic era within the Phanerozoic eon. The period within the Cenozoic that we live in is the Quaternary. The epoch within the period that we live in is the Holocene.
Dinosaurs and the Geological Time Scale...
Non-bird dinosaurs lived between about 245 and 66 million years ago, in a time known as the Mesozoic Era. This was many millions of years before the Homo sapiens, appeared.
Scientists divide the Mesozoic Era into three periods: the Triassic, Jurassic and Cretaceous.
The Triassic Period
(252-201 million years ago)
This began after Earth's worst-ever extinction event devastated life.
The Permian-Triassic extinction event, also known as the Great Dying, took place roughly 252 million years ago and was one of the most significant events in the history of our planet.
The Jurassic Period
(199.6 to 145.5 million years ago)
54-million-year chunk of the Mesozoic Era. Named for the Jura Mountains on the border between France and Switzerland, where rocks of this age were first studied, the Jurassic has become a household word with the success of the movie Jurassic Park.
The Cretaceous Period
(145 -66 million years ago)
The Cretaceous is a geological period that began 145 million years ago and ended 66 million years ago. It is the last period in the Mesozoic Era. It comes after the Jurassic Period and before the Paleogene - the first period of the Cenozoic Era, our current era.
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, although the exact origin and timing of the evolution of dinosaurs is a subject of active research.
Triassic dinosaurs evolved in the Carnian and include early sauropodomorphs and theropods. Most Triassic dinosaurs were small predators and only a few were common, such as Coelophysis, which was 1 to 2 metres long. Triassic sauropodomorphs primarily inhabited cooler regions of the world.
Next came the Predatory dinosaurs of the Jurassic included fearsome Allosaurus and Dilophosaurus. The Jurassic also saw the origination of the first birds, including the well-known Archaeopteryx, probably from coelurosaurian ancestors.
Lastly came the Cretaceous period this is the time of some of the most famous and well known dinosaurs, They included dinosaurs such as Tyrannosaurus Rex, Ankylosaurs, the one-headed pachycephalosaurs, Triceratops, and of course the velociraptor.
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